What is ‘The Rabbit Test’?

the rabbit test

Have you heard of The Rabbit Test?

We live in an age where determining if a woman is pregnant is incredibly simple. Go back a few decades, though, and the latest and greatest technology for determining whether a woman was with child involved a syringe full of urine and a little thing called The Rabbit Test.

the rabbit test

Yes, as crazy as sounds, you really can use animals like rabbits to detect whether a woman is pregnant. To be clear, this isn’t just an old wives’ tale that’s only correct just enough to keep people believing it. The Rabbit Test, is around 98.9% accurate (for reference, modern home pregnancy tests tend to range from 97%-99% in accuracy). Some version of this test has been the de facto way to test whether a woman was pregnant from the time the method was discovered in 1927, right up until the 1970s. The only real improvement made in that time being that, instead of a rabbit, later doctors used a specific species of frog. Maybe we’ll cover that another day…

The poor rabbits

the rabbit test

Simply, The Rabbit Test involved taking the urine of a woman who suspected she was pregnant and injecting it into a juvenile female rabbit. The importance of using a juvenile rabbit was that if the woman was pregnant, the rabbit would prematurely enter heat, which the doctor would be able to determine by checking its ovaries for certain signs, such as being enlarged with visible red dots on the surface.

This was a process that for the early days of the procedure unfortunately meant that the rabbit had to be killed, leading to a popular misnomer, and expression, that a woman would only be pregnant if “the rabbit died”; but in reality, the rabbit always died. It was believed for some time that the rabbit died due to pregnant woman’s hormones. However, it was in fact due to doctors having to remove the ovaries of the rabbit to inspect them. Resulting in the critters death.

the rabbit test

Much like with modern day pregnancy tests, the answer lies in the hormone human chorionic gonadotropin, commonly abbreviated to hGC. Produced by the placenta. hCG is (normally) only present in the urine of women who are pregnant or sometimes men who have testicular cancer. You can actually use pregnancy tests as a way to check for testicular cancer. Although, going to a doctor if you have any worries is preferable.

The history

Selmar Aschheim and Bernhard Zondek, a German gynecologist and endocrinologist, invented the Rabbit Test in the late 1920s respectively. Zondek, an expert in hormone research, discovered and isolated the hCG hormone while working alongside Aschheim, studying the urine of pregnant women in 1927. Noting that the hormone was (seemingly) only found in the urine of pregnant women (the fact that the hormone could be produced by testicular tumors, among others, was discovered a few years later), the pair correctly theorised that it was intimately linked with being pregnant, though they were never able to pinpoint where exactly it was produced, incorrectly proposing that it was produced by the anterior pituitary gland, rather than the placenta.

the rabbit test

After they managed to isolate the hormone, the men began experimenting with it to see what effect, if any, it would have on mice and rats. To their amazement, they discovered that it caused female rodents to begin ovulating, even if they hadn’t yet reached sexual maturity. How revolutionary this was cannot be overstated. By 1928, Aschheim and Zondek had perfected their rabbit test, dubbing it the A-Z test, as a nod to both of their names, and for the first time in all of human history, women who suspected they might be pregnant had a way to relatively quickly find out for sure.

In conclusion

If you were wondering why they chose rabbits over mice in the end, it’s simple. They chose rabbits because they were easier to handle than the mice, which made injecting them significantly easier.


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